Gas turbine engines are designed and operated at extremely high temperatures for the purpose of maximizing the efficiency. Such high temperatures pushes the materials used to the limits. Optimum operation and design is achieved with selective cooling of the various components.
High pressure air from the compressor is used and selectively directed through various components. The use of such cooling air bypasses the combustor and has a negative effect on gas turbine efficiency. Therefore it is desirable to achieve the required cooling with the minimum use of cooling air.
There are locations where a plurality of arcuate segments are used to define the gas flow path. The vane platforms is one such example. These vane platform segments must be segmented rather than being a single circle to permit differential expansion.
These segments are cooled by impinging cool air on the cold side of the segments. Where the segments join, it is conventional to cut a slot in each segment and place a thin metal feather seal in these slots between the two segments. The slot which accepts the feather seal breaks the heat flow path from the inside surface of the segment to the cooled outer side. Accordingly the segment is not sufficiently cooled at this feather seal location.
Various designs are known to selectively allow cooling flow through this area of the feather seal for the purpose of cooling the feather seal itself and the surrounding material of the segments.
It is desirable to achieve this cooling with the minimum negative effect on the gas turbine efficiency.